1. Open your .gpx file with Google Earth (right-click --> open with).
2. You will then see this window. Ensure all boxes are checked.
3. Expand out this file you just uploaded, leaving only the 'Path' visible.
4. Right-click on 'Path' then click Get Info. On the Style,Color tab you can change the appearance of your track. A thick red line shows up nicely.
5. Now right click on 'Path' again, and select 'Save Place As....' Select the file type KML and save.
6. Now go to maps.google.com and click on 'My Maps' then 'Create new map' (a Google account is required for this).
7. Type in a title & description, select whether to make it Public or Unlisted, then click on 'Import' to select the KML file.
8. After saving this map, you can click on 'Link' to allow other to find it (if Unlisted).